RISC-V: Stop emitting attributes

The RISC-V ELF attributes don't contain any useful information.  New
toolchains ignore them, but they frequently trip up various older/mixed
toolchains.  So just turn them off.

Tested-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230223224605.6995-1-palmer@rivosinc.com


Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>